Asymmetric Hetero Diels−Alder Reaction Catalyzed by Chiral Cationic Palladium(II) and Platinum(II) Complexes

Abstract

The hetero Diels−Alder reaction of nonactivated conjugated dienes 1 with arylglyoxals 2 and glyoxylate esters 7 proceeded enantioselectively in the presence of a catalytic amount of cationic chiral BINAP−palladium or −platinum complexes and 3 Å molecular sieves (MS3A). The addition of MS3A effectively improved the enantioselectivity of the reaction. Excellent ee's were obtained from the reactions of 2,3-dimethyl-1,3-butadiene (1a) and 1,3-cyclohexadiene (1d) with dienophiles 2 and 7. The square-planar structure of [Pd(S-BINAP)(PhCN)2](PF6)2 was determined by X-ray diffraction, and a chiral induction model involving the square-planar palladium complex coordinated with BINAP and a dienophile is proposed.

(R)- & (S)-2,2′-Bis(diphenylphosphino)-1,1′-binaphthyl

“…69a Arylboron compounds generated in situ from aryl bromides can be used as arylating reagents. 77 The catalytic enantioselective Baeyer-Villiger oxidation of substituted meso-cyclohexanones using 35% hydrogen peroxide as oxidant is achieved with [Pt(µ-OH)((R)-BINAP)] 2 (BF 4 ) 2 to give the corresponding lactones, although the yields are low (eq 48 69c A BINAP-Rh-catalyzed 1,4-addition of arylboronic acids to α,β-unsaturated amides provides optically active β-aryl amides.…”

Enantioselective [4+2] Cycloaddition of Buta‐1,3‐dienes to Alkyl Glyoxylates Catalyzed by the Chiral (Salen)Chromium(III) Complex

“…The NMR data of compounds 8a, 8b, 9a, 9b are in agreement with those described in the literature. [10] …”

“…[7] The [4 2] cycloadditions of simple 1,3-dienes, like buta-1,3-diene or cyclohexa-1,3-diene to highly activated carbonyl compounds, such as alkyl glyoxylates, were not so intensively investigated. There are in the literature only few reports on asymmetric version of this reaction, by Mikami×s, [8] J˘rgensen×s, [9] and Oi×s [10] groups, who successfully used chiral catalysts mainly based on a binaphthyl and bisoxazoline ligands.…”

Catalytic Asymmetric Hetero-Diels–Alder Reactions of Carbonyl Compounds and Imines

“…(20)]. [54] The HDA reaction proceeds well for reaction of phenylglyoxal 5 c with 2,3-dimethyl-1,3-butadiene (6 a) in the presence of the BINAP ligand and palladium(ii) and platinum(ii) salts giving 70 and 60 % yield, and 99 and 97 % ee, respectively, for the two Lewis acids. It is important that molecular sieves (3 ) are added to the reaction to achieve the high enantiomeric excess, especially for the chiral palladium(ii)-catalyzed reactions.…”